The present invention generally relates to a navigation system installed on a car for estimating a location at which the car is currently traveling. More particularly, the invention is concerned with a navigation system which is operatively interlocked with devices or units installed on the same car such as a communication unit exemplified by a transceiver, a device for detecting traveling conditions of the car and others.
The navigation system known heretofore has been designed for only one function of precisely displaying a position or location of a car at which the car equipped with the navigation system is currently traveling, as is disclosed, for example, in Japanese Patent Application Laid-Open No. 266219/1990 (JP-A-H2-266219).
A structure of a known navigation system for a car of the type mentioned above is shown in FIG. 20. As can be seen in this figure, the navigation system is composed of a processor in the form of a CPU 5 having a plurality of inputs supplied with output signals from an azimuth direction sensor 1 operating on the basis of terrestrial magnetism, a distance sensor 2 for detecting a distance covered by the car by measuring the rotation number of a wheel, an absolute position setting sensor 3 in the form of a radio receiver, and a CD-ROM (Compact Disk Read-Only Memory) 4.
In operation of the navigation system shown in FIG. 20, the traveling direction of the car is detected by the azimuth direction sensor 1 while the distance as covered is detected by the distance sensor 2. The absolute position setting sensor 3 receives a signal from a GPS satellite for determining an absolute reference position. The CPU 5 determines the current location of the car on the basis of the output signals from the azimuth direction sensor 1, the distance sensor 2 and the absolute position setting sensor 3 while referring to road network data (road map data) stored in the CD-ROM 4, wherein the location of the car is displayed on a display screen (not shown).
The known navigation system such as described above is designed only for the function of displaying the current traveling position or location of the car, but it is not in the position to detect, record and/or inform to others through radio communication and the like the occurrence of an accident which the car encounters in the course of traveling. Besides, the navigation system is equipped with none of the facilities for storing or recording the track or road history travelled by the car and the traveling or running condition, not to say of the means for recording the intra-car situation (state prevailing within the car) and personal information of the driver and passengers in the car such as names, addresses or the like. Moreover, the known car navigation system is not imparted with the capability of transmitting the information described above to relevant agencies or organizations such as police stations, a JAF (Japanese Automobile Federation Inc.) office or parties concerned. Such being the circumstances, the car involved in an accident is very difficult to locate. Moreover, great difficulty will be encountered in analyzing the cause of the accident. Needless to say, it is impossible or very difficult to inform the accident to liaison offices, organizations concerned such as mentioned above, or the parties concerned such as family or relatives or friends of the driver and/or the accompanying passenger.
Thus, there has long been a need for a system capable of monitoring the location of a car on a road and automatically emitting an accident signal when the car is involved in an accident. In a worst case scenario, if a car accident happened at night at which the event cannot be visually observed, it is vital that a message be sent out substantially immediately and automatically before the situation becomes too serious.